Tension-controlling means for traveling offset webs



March 17, 1931. c, B, CQTTRELL, 30 1,796,832

TENSION CONTROLLING MEANS FOR TRAVELING OFFSET WEBS Filed March 21, 1930 .29 50 a a; i? i 7 F H i INVENTOR WHHIH II llllll I H" II II U III W 2g ii J6 ATTORN EYS Patented Mar. 17, 1931 UNITED STATES PATENT OFFICE CALVERT B. COTTI B I ELL, 31), F WESTEBLY, RHODE ISLAND, ASSIGNOR TO C. B. COTTRELL & SONS COMPANY, OF WESTERLY, RHODE ISLAND, A CORPORATION OF DELAWARE TENSION CONT1t-OLLING MEANS FOR TRAVELING OFFSET WEBS Application filed March 21, 1930. Serial No. 437,820.

In rotary multicolor web perfecting printing presses where a traveling offset web is passed around the impression cylinder of the second printing unit under the printed web,

it has been difficult to obtain clean and sharp printing. I If this tension on the offset web, necessary to the proper rewinding thereof, be eliminated where the offset web is in contact with the impression cylinder, the offset web and the printed web will travel together around the impression cylinder, thereby ensuring clean and sharp printing by the second print- V ing unit.

r The object of my invention is to accomplish this result by providing automatic means for maintaining a predetermined amount of slack in and tension, on the offset web between theimpression cylinder of the second print- 7 ring unit of the printing press and the tension control rolls of theoffset web tension controlling mechanism for the rewinding mechanism. p a 1; The means which I have shown for accomplishing this result includes a variable speed drive for the offset web tension controlling mechanism and a normallyinactive reversible motor for intermittently operating the variable speed drive; which motor is started in either direction and stopped by a controller in the motor circuit, which controller is operated by a web slack roller as the roller rises '01 drops, due to the lessening or lengthening of the slack in the offset web between the printing unit and the offset web tension controlling mechanism.

In. practice, the travel of the printed web per cylinder revolution varies with the differout forms used on the form cylinders, thus making it practically impossible toproperly proportion the tension control rolls of the offset web controlling mechanismso that they will travel with the offset web under all conditions. It is to prevent this variationfrom disturbing thetravel of the offset web on the impression cylinder that I interpose the means for automatically maintaining a predetermined amount of slack in and tension on the offset web between the impression cylin' and to and around the positively driven tender of the second printing unit and the said tension control rolls.

A practical embodiment of my invention is represented in the accompanying drawings, in which Fig. 1. represents a diagrammatic side elevation of that portion of a multicolor Web perfecting printing press which embodies my invention; and

Fig. 2 represents a detail top plan view, showing the variable speed drive unit for the offset web tension controlling mechanism.

The form and impression cylinders of the second printing unit are denoted by 1, 2, 3,

4 and 5, which cylinders are driven in the 5 usual manner. a

The traveling printed web is denoted by 6 and it is shown as being led around the idler roll 7 to and around the impression cylinder 5 and from thence around the printed 7 0 web guide roller 8.

The traveling offset web is denoted by 9 and it is shown as leading from its supply roll lOover the idler roll 11 to and around the impression cylinder 5 and under the printed web 6. From thence the offset web is shown as passing around the positively driven guide roll 12 and under the web slack roller l3 where the slack in the web is formed,

so sion control rolls 14, 15, 16 of the offset web tension controlling mechanism. From thence the offset web passes around theidler rolls 17, 18 and 19 to the take-up roll 20 which rests upon and is driven by the rcwinding 8 rolls 21, 22 of the offset web rewinding mecha nism.

The guide roll 12 is shown as being driven from the impression cylinder gear 23 at sub stantially the surface speed of the impresflfi sion cylinderathrough the train of gears 24;,

The offset web rewinding rolls 21, 22 are shown as driven at a slightly greater surface speed than the impression cylinder so p as to exert a slip feed effecton the offset web to ensure its tight winding on the take-up roll 20 under the control of the tension control rolls 14, 15, 16 of the offset web tension controlling mechanism. In the present instance we these rewinding rolls 21, 22 are shown as being driven from the gear 29 on the shaft of the gear 25, through a train of gears 30 to 37 inclusive. 5

A variable speed drive of any well known or approved form is provided for driving the offset web tension control rolls 14, 15, 1'6 of the offset web tension controlling mechanism, the variable speed drive represented herein the shaft 3 8i's driven at a constant speed by the meshing of its gear 39 with'the gear 33 of the trainof gears leading from the second printing unit to theoffset WGb rewinding mechanism. The shiftable cone pulleys 40 on the constant speed shaft 38 drive the shiftable cone pulleys 41 on the shaft 42 which is coupled to the shaft of the tension roll 14,

7 through the usual belt 43. I

The automatic means which I have provided for varying the speed of the shaft 42 comprises a normally inactive screw shaft 44', connected in the usual manner by the oppositely working levers 45, 45* for shifting the cone pulleys 40 and 41." This normally inactive screw shaft 44' is provided with a normally inactive reversible motor45**, the starting and stopping of which is controlled hy'the undue lessening or lengthening of the slack in the offset webbetween the second printing unit and the Web tension controlling mechanism, as will hereinafter appear.

A predetermined amountof slack in the offset web between the impression cylinder of the second printing unit and the tension control rolls 14, 15, 16 of the offset web tension controlling mechanism is automatically maintained by starting the normally inactive motor, 45 in eitlierdirection and thereafter stopping the same, to increase or diminish the surface speed of the said tension control rolls as followsz r The offset web slack roller 13 is mounted in a rocking support 46, to which support circuit,- denoted by 56 of the motor 45. This arm 54 is normally maintained, by the requisite amount of slack in the offset 'web9, in a neutral position. As the slack in the web decreases, thearm 54 will swing in a direction to'finally engage the Contact '57, to

drive the motor 45 momentarily in' a directhe web slack a increase. As the slack in the crises web increases", the controller arm I 54 will a direction to fiiial-ly env p t, I V V a p H trolling. mechanism. tlon to 'red'uce'the surface speed of the web tension control rolls 14, 15, 16 and" cause gage the contact 58, to drive the motor 45 momentarily in the opposite direction to increase the surface speed of the web tension control rolls and cause the web slack to decrease.

- The predetermined tension is maintained on the offset web sla'ckbetween the'second printing unit and the web tension controllin mechanism as follows: being the well known liee'ves drive 1n winch f K roll 59 bears on the offset web as it passes over the first tension controlroll 14, with sufficient pressure to eliminate, any slippage of the web as it passes through the web tension controlling mechanism. As the only tension exerted on the web slack is formed by the pressure of the web slack roller 13 thereon, this tension can be easily regulated by increasing or diminishing the effect of the counterbalanced weight 'on the said roller.

From the above description it will be seen that a predetermined amount of slack and tension may be automatically maintained in its rewinding mechanism; a web tension controlling mechanism, and a variable" speed drive therefor driven-from the printing unit and controlled by varlatlons msthe amount 2; In a multicolor web perfecting printing press,- a rinting unit, a traveling ofl'set web, its rewinding mechanism driven from the printing unit, a web tension controlling mechanism, and a variahle'speed drive there for driven froin the printing unit and controlled by variations in the amount of slack jof slack in the ofi'setweb between the print- 'ing unit andweb tension controllingmechaiii) in the' o'ffset' web between the printingunit and web tension controlling mechanism.

3. In a multicolor web perfecting printing press, a printing unit, a traveling offset web, its rewindi'ng mechanism,- aweb tension controlling mechanism, avariable speed. drive therefor driven fromthe printing unit,- and automatic means controlling. the. variable speed drive for maintaining a. predetermined amount ofweb slack and tension thereon between the printing unit and the tension controlling .infe'cjlianisin, a variable spa-ea drive therefor driven from an printing use, and

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automatic means controlling the variable speed drive for maintaining a predetermined amount of web slack and tension thereon between the printing unit and the tension controlling mechanism, said automatic means including a normally inactive motor for said drive.

5. In a multicolor web perfecting )rinting press, a printing unit, a traveling 0 set web, its rewinding mechanism, a web tension controlling meehanism, a variable speed drive therefor driven from the printing unit, and automatic means controlling the variable speed drive for maintaining a predetermined amount of Web slack and tension thereon between the printing unit and the tension controlling mechanism, said automatic means including a normally inactive motor for said drive and also including a web slack roller for indirectly causing the starting and stopping of the motor.

6. In a multicolor web perfecting printing press, a printing unit, a traveling offset web, its rewinding mechanism, a web tension controlling iechanism, a variable speed drive therefor driven from the printing unit, and automatic means controlling the variable speed drive for maintaining a predetermined amount of web slack and tension thereon betweentlie printing unit and the tension controlling mechanism, said automatic means including a normally inactive motor for said drive and also including a web slack roller and a controller in the motor circuit operated by the roller for starting and stopping the motor.

7. In a multicolor web perfecting printing press, a printing unit, a traveling offset web, its rewinding mechanism, a web tension controlling mechanism, a variable speed drive therefor, a normally inactive motor for said drive, and web slack controlled means for automatically maintaining, through said motor, a predetermined amount of slack in and tension on the web between the printing unit and tension controlling mechanism.

8. I11 a multicolor web perfecting printing press, a printing unit, a traveling ofl'set web, its rewinding mechanism, a web tension controlling mechanism, a variable speed drive therefor; a normally inactive motor for said drive, and web slack controlled means for automatically maintaining, throi'lgh said motor, a predetermined amount of slack in and tension on the web between the printing unit and tension controlling mechanism, said means including a Web slack roller.

9. In a multicolor Web perfecting printing press, a printing unit, a traveling offset web, its rewinding mechanism, a web tension controlling mechanism, a variable speed drive therefor, a normally inactive motor for said drive, and web slack controlled means for auton'iatically maintaining, through said motor, a predetermined amount of slack in and tension on the web between the printing unit and tension controlling mechanism, said means including a web slack roller and also including a controller in the motor circuit, operated by the roller for starting and stop ping the motor.

10. In a multicolor web perfecting printing press, a printing unit, a traveling otl'set web, its rewinding mechanism, a train of gears connecting the printing unit and rewinding mechanism, a web tension controlling mechanism, a variable speed drive unit connecting said train of gears with the web tension controlling mechanism, a normally inactive motor for said unit, and web slack controlled means for automatically maintaining, through said motor, a predetermined amount of slack in and tension on the offset web between the printing unit and tension controlling mechanism.

ll. In a multicolor web perfecting printing press, a printing unit, a traveling otl'set web, its rewinding mechanism, a train of gears connecting the printing unit and. rewinding mechanism, a web tension control ling mechanism, a "ariable speed drive unit connecting said train of gears with the web tension controlling mechanism, a normally inactive motor for said unit, and web slack controlled means for automatically maintaining, through said motor, a predetermined amount of slack in and tension on the offset web between the printing unit and tension controlling mechanism, said means including a web slack roller.

12. In a multicolor web perfecting printing press, a printing unit, a traveling offset web, its rewinding mechanism, a train of gears connecting the printing unit and rewinding mechanism, a web tension controlling mechanism, a variable speed drive unit connecting said train of gears with the web tension controlling mechanism, a normally inactive motor for said unit, and web slack controlled means for automatically maintaining, through said motor, a predetermined amount of slack in and tension on the offset web between the printing unit and tension controlling mechanism, said means includ ing a web slack roller and also including a controller in the motor circuit, operated by the roller, for starting and stopping the motor.

In testimony, that I claim the foregoing as my invention, I have signed my name this 14th day of March, 1930.

CALVERT B. COTTRELL, 3RD. 

